This application addresses broad Challenge Area (01) Behavior, Behavioral Change, and Prevention and specific Challenge Topic, 01-AA-103: Capturing Social Network Information for Groups at High Risk for Negative Health Behaviors. NIH has identified the Internet as a promising prevention and research modality given its appeal among young adults (YAs), its suitability for advancing prevention research, and its unique capability to diffuse prevention programs to large numbers of YAs residing in numerous geographic locations (Pequegnat, et al., 2007). Parallel to the escalation of e-technology, researchers have sought to understand the Internet's role in young adults'risk-taking behaviors. Informed by a Social Influence and Integration Model of AOD use, we contribute to the growing body of research methods to capture social network data via the Internet and assess innovative strategies to maximize the internal and external validity of web-based findings in an ethnically-diverse sample of youth transitioning into young adulthood (ages 18 to 24). Our Specific Aims are to (1) Implement a WebRDS strategy to recruit YAs to participate in a web-survey of AOD use, and describe the recruitment and outcomes through virtual networks;(2) Characterize YAs and their virtual networks in terms of network size and cohesion, demographic composition of network members, prevalence of AOD and AOD-related activity among network members, and provision of social support, and (3) Examine the influence direct and indirect associations between YAs'virtual network characteristics and YAs'AOD use, separately and concurrently with sexual activity. We employ ego-centric network analyses and structural equation modeling to test these issues. If successful, we will diffuse our WebRDS program to research and community partners. Section 7. Project Narrative This application addresses broad Challenge Area (01) Behavior, Behavioral Change, and Prevention and specific Challenge Topic, 01-AA-103: Capturing Social Network Information for Groups at High Risk for Negative Health Behaviors. We contribute to the growing body of research methods to capture social network data via the Internet and assess innovative strategies to maximize the internal and external validity of web- based findings in an ethnically-diverse sample of youth transitioning into young adulthood (ages 18 to 24).